Eurybia divaricata

Source: Wikipedia, the free encyclopedia.

White wood aster

Secure  (NatureServe)[1]
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Asterales
Family: Asteraceae
Genus: Eurybia
Species:
E. divaricata
Binomial name
Eurybia divaricata
(
G.L.Nesom
Natural range in North America
Synonyms
Synonymy
  • Aster boykinii E.S.Burgess
  • Aster carmesinus E.S.Burgess
  • Aster castaneus E.S.Burgess
  • Aster claytonii E.S.Burgess
  • Aster corymbosus Sol. ex Aiton
  • Aster divaricatus L.
  • Aster elatus Bertero ex Steud.
  • Aster excavatus E.S.Burgess
  • Aster fischeri Kuntze
  • Aster flexilis E.S.Burgess
  • Aster stilettiformis E.S.Burgess
  • Aster tenebrosus E.S.Burgess
  • Biotia corymbosa var. alata (W.P.C.Barton) DC.
  • Eurybia corymbosa (Sol. ex Aiton) Cass.

Eurybia divaricata (syn. Aster divaricatus), the white wood aster, is an herbaceous plant native to eastern North America. It occurs in the eastern United States, primarily in the Appalachian Mountains, though it is also present in southeastern Canada, but only in about 25 populations in the provinces of Ontario and Quebec. In the U.S. it is abundant and common, but in Canada it is considered threatened due to its restricted distribution. It has been introduced to a number of countries in Europe.[2] It can be found in dry open woods as well as along wood-edges and clearings. The species is distinguished by its flower heads that have yellow centers and white rays that are arranged in flat-topped corymbiform arrays, emerging in the late summer through fall. Other distinguishing characteristics include its serpentine stems and sharply serrated narrow heart-shaped leaves. The white wood aster is sometimes used in cultivation in both North America and Europe due to it being quite tough and for its showy flowers.

Description

Eurybia divaricata is a late summer to fall-flowering herbaceous

involucres, and only occurs in the southern U.S. from Virginia to Georgia.[3]

Three types of

margins of the leaf, while the apices, or tips of the leaves, are acuminate, meaning they taper to a point. The adaxial (i.e. upper) surfaces of the leaves are nearly hairless or sparsely hairy, while the abaxial (i.e. lower) surfaces are sparsely hairy with the veins being more villous, or covered in shaggy hairs.[3]

The basal leaves are

lanceolate, meaning lance-shaped, with rounded bases and are 0.5 to 2 cm (0.20 to 0.79 in) long by 0.1 to 0.8 cm (0.039 to 0.315 in) wide.[3]

The

pappi.[3]

1913 line drawing[4]

The

phyllaries, which are the small leaves that make up the involucre, number from 25 to 30 and are arranged in 4 to 5 series. The inner phyllaries are between linear and lanceolate in shape with a purplish colouration towards the apices, while the outer ones are more oblong. All of the phyllaries are strongly unequal with hardened bases, margins that are somewhat scarious (i.e. thin, membranous and dry) as well as fimbriate-ciliate, meaning fringed with hair at the margins. Their apices are rounded to acute in shape, while the surfaces are sparsely haired, though sometimes sparsely covered in stipular glands. Their chlorophyllous zones, a darker green zone where chlorophyll is concentrated, appear on the upper half of the outer phyllaries, to the upper third or along the outer midveins of the inner phyllaries. The outer phyllaries typically measure 0.7 to 1.5 mm (0.028 to 0.059 in) wide with the lengths rarely exceeding 2.5 times the width.[3]

As with most members of the family

corollas (i.e. petals, though they are fused into a tube) that are 4.1 to 4.8 and exceptionally 5.5 mm long. Their corollas are abruptly ampliate, or enlarged, with tubes that are longer than their campanulate throats. The tubes measure 2.3 to 2.6 mm while the throats are typically only 0.9 to 1.2 mm long. The lobes, i.e. the friges of the throat, are reflexed and lanceolate in shape, measuring 0.7 to 1.4 mm.[3]

The fruit are

sepals, are made up of reddish to cream-coloured bristles that are 3.7 to 5 mm (0.15 to 0.20 in) long, making them equal to or longer than the disc corollas in length. The bristles are fine and barbellulate, or barb-like, though they may be sometimes more or less clavate, or club-shaped, towards their apices.[3]

Similar species

Several different plants are superficially quite similar to the white wood aster, but close examination as well as knowledge of the plants' differing habitats and ranges can readily distinguish them. The most similar species is the mountain wood aster (Eurybia chlorolepis), which was previously considered conspecfic with E. divaricata. E. chlorolepis differs in having flower stalks that are longer than 1.5 cm, while those of E. divaricata are shorter than this. The involucres of the mountain wood aster are generally between 6.5 and 9 mm in length, while those of the white wood aster are normally from 4.2 to 6.5 mm long, but in rare cases they may be as long as 7.5 mm. The mountain wood aster almost always has more rays than the white wood aster: the former usually has 12 to 16, but occasionally as few as 10, while the latter generally has 5 to 10 and never more than 12. The rays are also longer on the mountain wood aster at 17 to 18 mm in most cases, while the white wood aster's are generally only 10 to 15 mm. Lastly, E. chlorolepsis is present only from southern Virginia south to Georgia in the Appalachian Mountains at altitudes of 1,200 to 2,000 m (3,900 to 6,600 ft), while E. divaricata can be found from southern Canada south to Alabama, meaning their ranges only overlap in the southern United States, and there only at high elevations.[5]

Another species commonly confused with the white wood aster is Schreber's aster (Eurybia schreberi). Schreber's aster is typically found on moister soils, though it can also be found on mesic sites. While much of their ranges overlap, Schreber's aster is not found south of Virginia or Tennessee. Schreber's aster can also be distinguished by the more numerous teeth on the leaves, typically numbering 15 to 30 per side to the white wood aster's 6 to 15 per side. The leaves are wider on Schreber's aster with broader sinuses at the bases. The flower stalks are also densely hairy on the white wood aster, while they are only sparsely haired on Schreber's aster. Lastly, the clones of E. schreberi have sterile rosettes, while those of E. divaricata do not.[5]

Two other superficially similar plants include the bigleaf aster (Eurybia macrophylla) and the heartleaf aster (Symphyotrichum cordifolium), though both usually have blue or pale blue rays, while those of E. divaricata are always white. Both species sometimes have white rays in rare cases, but E. macrophylla can still be distinguished by its larger and broader leaves and S. cordifolium by its straighter and branched stems.[5][6]

Distribution and habitat

Eurybia divaricata is present primarily in the

the Netherlands.[3]

The species is known from only 25 locations in Canada, and is considered threatened.[8]

Cultivation and uses

While the white wood aster does not compare in popularity to the other cultivated asters, such as the

New England aster, it does have its niche, especially in North American native gardens. The plant flowers earlier than many other asters, does not require any staking to support it and flowers well in shade. It is attractive to gardeners due to its showy white flowers that emerge in mid to late summer, its prostrate habit, as well as its hardiness and the minimal maintenance it requires. It has little problem with both disease and insects. They do require partial shade, however, and they perform best when given about 4 hours of sunlight. The plants can be cut to 20 cm (8 in) in the spring in order to delay flowering and increase the number of branches. It is marginally hardy in USDA zone 3, and fully hardy from zones 4 to 8. It is commonly available in North American nurseries and several cultivars have been selected, including:[9]

The young leaves of the plant can be cooked and eaten.[10]

References

  1. ^ "Eurybia divaricata". NatureServe Explorer. NatureServe. Archived from the original on 2007-09-29. Retrieved 2007-06-13.
  2. ^ "Eurybia divaricata (L.) G.L.Nesom". Plants of the World Online. Royal Botanic Gardens, Kew. Retrieved 11 December 2022.
  3. ^ a b c d e f g h Brouillet, Luc (2006). "Eurybia divaricata". In Flora of North America Editorial Committee (ed.). Flora of North America North of Mexico (FNA). Vol. 20. New York and Oxford: Oxford University Press – via eFloras.org, Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.
  4. ^ illustration from Britton and Brown's Illustrated flora of the northern states and Canada, 1913, as Aster divaricatus
  5. ^ a b c Brouillet, Luc (2006). "Eurybia". In Flora of North America Editorial Committee (ed.). Flora of North America North of Mexico (FNA). Vol. 20. New York and Oxford: Oxford University Press. Retrieved June 27, 2007 – via eFloras.org, Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.
  6. ^ Brouillet, Luc; Semple, John C.; Allen, Geraldine A.; Chambers, Kenton L.; Sundberg, Scott D. (2006). "Symphyotrichum cordifolium". In Flora of North America Editorial Committee (ed.). Flora of North America North of Mexico (FNA). Vol. 20. New York and Oxford: Oxford University Press. Retrieved June 27, 2007 – via eFloras.org, Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.
  7. ^ "Eurybia divaricata". County-level distribution map from the North American Plant Atlas (NAPA). Biota of North America Program (BONAP). 2014.
  8. ^ COSEWIC (2002). "COSEWIC assessment and update status report on the white wood aster Eurybia divaricata in Canada" (PDF). Canadian Wildlife Service. Retrieved 2007-06-22.
  9. ISBN 0-88192-760-0
    .
  10. ISBN 0-394-50432-1
    .

External links
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